Recording Live Playback using ALSA

Kapil Hari Paranjape

June 1, 2006

Have you ever felt the urge to record some “live” music while you are listening to it? The following procedure might do what you want.

Prerequisites: The sound on your computer should use a 1.x release of the ALSA drivers (say Linux version 2.6.x) and you have alsa-lib (Debian’s libasound2) installed.

Assumptions: You don’t already have a $HOME/.asoundrc file. If you do then you need to edit it suitably. You also should not have a script/program called recording :-).

Result: You run recording -on to start recording. You then start your live playback. After you have had enough you stop the live playback. You then run recording -off and are left with a (large) file containing the recording.


  1. First create a file called $HOME/.asoundrc like the enclosed asoundrc.txt.
  2. Create the links.
            ln -s /dev/null /var/tmp/null.raw  
            ln -s /var/tmp/null.raw /var/tmp/record.raw

  3. Next install a script recording somewhere in the search path for executables for your shell. This script should look like the enclosed recording.txt.
  4. That’s it!


  1. This only works for digital live playback through the PCM device of your soundcard. You can use arecord for the other devices since these can usually be “captured”.
  2. Don’t forget to copy/convert your recording /var/tmp/sound.raw to a safe location.
  3. This only works with audio players that support ALSA plugins. To get it to work with other players like realplay, install alsa-oss and use aoss realplay instead of realplay.
  4. You usually cannot run recording -on/-off while the player has the audio device open. For many players (in particular those like (3) above), you must quit the player before and after recording.
  5. The supplied asoundrc converts the incoming audio to CD format. This may lead to a loss in quality but I prefer it to guessing the real format of the raw data in each case.
Have Fun!